1. Field of the Invention
The present invention deals with automatic toilet flushers and in particular with the criteria used do control them.
2. Background Information
Automatic flow-controls systems have become increasingly prevalent, particularly in public rest-room facilities. Automatic flushers contribute to hygiene, facility cleanliness, and water conservation. In such systems, object sensors detect the user and operate a flow-control valve in response to user detection. Most such detectors are of the infrared variety. They transmit infrared light into a target region, sense infrared light reflected from a user, and base detection decisions on the reflection percentage. Detection of the fact that a user has approached the toilet and then left is typically what triggers flushing action. (We use the term toilet in a broad sense to include what are variously called toilets, urinals, water closets, etc.)
Most automatic flushers work with enough reliability to make them valuable for the reasons just mentioned; if the flusher occasionally fails to flush in response to one use, it usually happens that it flushes in response to the next. Still, such an occasional failure tends to impose upon that next user""s sensibilities.
We have devised a way of increasing the flusher""s reliability. The reason for an automatic flusher""s failure to respond In accordance with the invention, the response depends on reflection-percentage changes but is independent of absolute reflection percentage. That is, the control circuit does not base its determination of whether the user has approached the toilet on whether the reflection percentage has exceeded a predetermined threshold, and it does not base a determination of whether the user has withdrawn from the toilet on whether the reflection percentage has fallen below a predetermined threshold. Instead, it is based on whether a period in which the reflection percentage decreased (in accordance with appropriate withdrawal criteria) has been preceded by a period in which the reflection percentage increased (in accordance with appropriate approach criteria).